Beaming microwave energy to earth from orbiting solar panels (see this month’s news and EPRI Journal spring 2000) might be an option in the very long term, but for the foreseeable future the world’s energy needs will have to be met from rather more down-to-earth sources.
The dramatic rise of natural gas fuelled electricity generation – driven by favourable economics and environmental factors – has of course been a dominant feature of the electricity business in recent years, but coal is still the mainstay of power generation worldwide. According to a recent report from the World Coal Institute, some 37 per cent of the world’s electricity is generated from coal, about twice the figure for natural gas, although that is rising sharply.
Coal is abundant and widely distributed around the world, notably in key developing countries such as China, India, Indonesia and South Africa. If low grade coal and mining residues, eg from coal washing, are taken into account – which constitute a significant fuel reserve in places like the Ukraine, Eastern Europe and India and whose potential can be unlocked with fluidised bed boilers – the amounts grow even further.
It is not an energy source we can walk away from lightly. The challenge is to use the vast resource that coal represents in a way that is environmentally acceptable as well as economic. There is immense room for improvement. For example, the average efficiency of Chinese coal fired power plants, which are relatively small, is a meagre 28 per cent compared with an average of 38 per cent for the OECD countries.
In the USA, coal accounts for some 56 per cent of electricity generation, but according to a recent EPRI study (also reported in this month’s news) a large proportion of currently operating coal plants will not be able to withstand the expected onslaught from the combined effects of of emissions control, air quality and climate change policies.
The EPRI study, called E-EPIC (which stands for Energy–Environment Policy Integration and Co-ordination), is essentially an extrapolation of current US policy directions to their logical conclusion. It suggests that future restrictions on carbon dioxide, nitrogen oxides and sulphur dioxide will cause the proportion of electricity derived from coal in the United States to decline to a mere 10 per cent by 2020. This is of course further good news for gas turbine makers – already enjoying an unprecedented glut of orders. EPRI projects that the share of gas in electricity generation would rise from 15 per cent to 60 per cent, requiring an investment of no less than $160 billion in new gas-fired generating plants and causing “many viable coal-fired generating plants to fall into disuse, thereby stranding investments in not only the plants, but also recently installed emission control equipment.” However, such a reliance on natural gas could not be sustained. The EPRI study projects that the increasing demand it hypothesises would cause natural gas prices to rise, prompting a shift to alternatives, including biomass, wind, clean coal and even new nuclear plants. EPRI concludes that better co-ordination is needed between requirements on emissions reduction and available technology, suggesting that an extension of the schedule for emissions reduction combined with aggressive R&D will be needed if the USA is to avoid dramatic shifts in fuel use, loss of productive use of energy assets and cost escalation.
This is all hypothesis of course and it is looking a long way ahead, but EPRI is not alone in worrying about overdependence on gas and the potential for natural gas price rises.
Concerns about natural gas availability, albeit some way into the future, would certainly give a boost to the clean coal community, for example protagonists of coal gasification. With gas prices low, the economics of deploying such advanced clean coal technologies have not been attractive. But all that could change if gas prices should rise significantly, as has been predicted by some forecasters, and if some costs could be lopped out of the technologies themselves.
In May, Southern Company, the USA’s largest electricity producer and biggest coal user, together with the US Department of Energy, announced they had “reached a milestone” in this direction with successful production of gas from coal using an air-blown transport reactor at the Power Systems Development Facility, Wilsonville, Alabama.
Because of its compactness, simplicity and higher efficiency, researchers at Wilsonville claim great benefits for their transport reactor technology over other coal gasification systems – a view not necessarily shared by other gasification specialists who prefer oxygen blown systems with air separation units.
“Our goal is to make coal both cost competitive and environmentally comparable to natural gas and we’re almost there,” reckons Charles Goodman, Southern’s vice president for research and environmental affairs. Whether he’s right or not should be settled pretty soon as Southern Company believes it will be in a position as early as next year to decide whether to proceed to a commercial power plant using the transport reactor.